[FASM] Compare 2 strings

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(12-02-2016, 12:39 AM)Jochen Wrote:

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I would just do:

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^ full manual approach using pointer arithmetic and comparing null-byte with test.

Essentially my approach was to load the address of the string into ecx, load the address of the string offset by 1 into edx (because of the last inc to ecx before the test), compare bytes from ecx register by moving them into lower eax (al) 8-bit segment, then subtract edx (string address + 1) from ecx to get the length. In the case of "", ecx is still incremented, which will match edx+1 to return 0.

I would just do:

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^ full manual approach using pointer arithmetic and comparing null-byte with test.

Essentially my approach was to load the address of the string into ecx, load the address of the string offset by 1 into edx (because of the last inc to ecx before the test), compare bytes from ecx register by moving them into lower eax (al) 8-bit segment, then subtract edx (string address + 1) from ecx to get the length. In the case of "", ecx is still incremented, which will match edx+1 to return 0.

Hi bitm0de: Your talking about getting the length of a string ?
For that i use this atm

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(12-05-2016, 10:30 AM)Jochen Wrote:

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I would just do:

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^ full manual approach using pointer arithmetic and comparing null-byte with test.

Essentially my approach was to load the address of the string into ecx, load the address of the string offset by 1 into edx (because of the last inc to ecx before the test), compare bytes from ecx register by moving them into lower eax (al) 8-bit segment, then subtract edx (string address + 1) from ecx to get the length. In the case of "", ecx is still incremented, which will match edx+1 to return 0.

Hi bitm0de: Your talking about getting the length of a string ?
For that i use this atm

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Ahh yeah. Correct. Change test to a cmp and increment an offset to another memory space for comparison. I don't know why I read this as Strlen rather than Compare... :S This would be the naive version of it though, the actual implementation of strlen() is not so simple, and involves a lot of bitwise arithmetic tricks:

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My ASM is very small byte size though too.

You like using all of the special string instructions over doing things manually don't you?

You like using all of the special string instructions over doing things manually don't you?

I like to learn new things. I find ASM interesting because you can understand the inner workings of things :smile:
I first started out with Delphi. I would like to learn C/C++. If you want to create big stuff you can't always rely on ASM.
Delphi create big PE files with many sections. I believe you can control that in C/C++ ? (FileSize) etc ..
And i always can use inline ASM under C/C++ to.. BitmOde can you give me a few tips to get started ? What compiler do you use ? Btw i dont like Visual Studio

(12-06-2016, 01:09 AM)Jochen Wrote:

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You like using all of the special string instructions over doing things manually don't you?

I like to learn new things. I find ASM interesting because you can understand the inner workings of things :smile:
I first started out with Delphi. I would like to learn C/C++. If you want to create big stuff you can't always rely on ASM.
Delphi create big PE files with many sections. I believe you can control that in C/C++ ? (FileSize) etc ..
And i always can use inline ASM under C/C++ to.. BitmOde can you give me a few tips to get started ? What compiler do you use ? Btw i dont like Visual Studio :smile:

The language has less to do with PE output and it's more compiler based. Saying you can achieve better control over file alignment and section size is not a programming language dependent matter IMO. You can always manipulate the PE after it's gone through compilation.

Visual Studio is an IDE though but if you're on Windows, it would be my suggestion for C++, if you want to do C, then just grab a build of MinGW for gcc.

(12-06-2016, 03:53 AM)bitm0de Wrote:

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(12-06-2016, 01:09 AM)Jochen Wrote:

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You like using all of the special string instructions over doing things manually don't you?

I like to learn new things. I find ASM interesting because you can understand the inner workings of things :smile:
I first started out with Delphi. I would like to learn C/C++. If you want to create big stuff you can't always rely on ASM.
Delphi create big PE files with many sections. I believe you can control that in C/C++ ? (FileSize) etc ..
And i always can use inline ASM under C/C++ to.. BitmOde can you give me a few tips to get started ? What compiler do you use ? Btw i dont like Visual Studio :smile:

The language has less to do with PE output and it's more compiler based. Saying you can achieve better control over file alignment and section size is not a programming language dependent matter IMO. You can always manipulate the PE after it's gone through compilation.

Visual Studio is an IDE though but if you're on Windows, it would be my suggestion for C++, if you want to do C, then just grab a build of MinGW for gcc.

Okay thx